This invention relates to a compensator for use in a pulse noise cancelling circuit. The compensator is specifically useful in a radio receiver for an automobile or the like.
In a radio receiver of the type described, a received input signal is inevitably accompanied by noise pulses owing to a signal device, ignition devices, and so on. In order to cancel the noise pulses, a conventional noise pulse cancelling circuit detects the noise pulses to thereby interrupt the received input signal during duration of the each detected noise pulse and to produce an output signal free from the noise pulses. In this cancelling circuit, an interruption takes place in the output signal as a result of suppression of the noise pulse. Alternatively, it is known in the art to retain or hold, during presence of the noise pulse, a level of the input signal just before occurrence of each noise pulse so as to remove the noise pulse. However, discontinuity inevitably occurs in the output signal. Reduction of tone quality results from the discontinuity of the output signal.
It is known that the reduction of tone quality due to the discontinuity is distinctly sensible or audible in a comparatively low frequency band less than about 1 KHz. This means that the reduction of tone quality primarily depends on the discontinuity in the low frequency band.